As disclosed in Japanese Unexamined Patent Publication No. H7-20534 and Japanese Utility Model Publication No. H6-26897, a typical focal plane shutter comprises two sector groups each having a plurality of sectors supported by arms constituting a parallel link and an opening formed in a shutter base plate is opened or closed by operating the two sector groups. The sectors of the sector groups have connecting pins fixed thereto by caulking, and the sectors are pivotally supported by the arms with the connecting pins pivotally fitting in through-holes drilled through the arms. Further, when the sectors are folded, the outer edge portion of one of the sectors is interposed between one of the arms and another sector supported by the arm at a position close to the connecting pin connecting the arm and the other sector.
A focal plane shutter having the above-described structure has one disadvantage in that when the sector groups are folded, the edge portion of a sector sometimes becomes jammed between one of the arms and another sector connected to the arm through a connecting pin. In view of the recent trend of reducing the thickness and size of the camera to meet an increased demand for weight reduction and increased speed, the space between the adjoining sectors has inevitably become more narrow, resulting in the adverse effect of causing such jamming. That is, a problem has arisen in that during the initial stage of a closing operation of the shutter, the frictional resistance of the jammed sector increases to such an extent that there is a difference in moving characteristics between the in jammed sector and other sectors which are free of such jamming, resulting in a reduction in the exposure performance of the shutter. To solve this problem by reducing the thickness of each of the sectors has, been difficult, however, in view of the requisite high strength and light shielding properties thereof.